[PATCH 1/2] nohz: Drop useless call in tick_nohz_start_idle()

[PATCH 1/2] nohz: Drop useless call in tick_nohz_start_idle()

[Frederic Weisbecker]

The call to update_ts_time_stats() there is useless. All
we need is to save the idle entry_time.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 kernel/time/tick-sched.c |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d5097c4..58e1a96 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -185,9 +185,6 @@ static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
 	ktime_t now;
 
 	now = ktime_get();
-
-	update_ts_time_stats(cpu, ts, now, NULL);
-
 	ts->idle_entrytime = now;
 	ts->idle_active = 1;
 	sched_clock_idle_sleep_event();
-- 
1.7.5.4

[PATCH 2/2] nohz: Drop ts->idle_active

[Frederic Weisbecker]

ts->idle_active is used to know if we want to account the idle sleep
time. But ts->inidle is enough to check that.

So drop that field and use inidle instead. This simplifies the code.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/tick.h     |    1 -
 kernel/time/tick-sched.c |   14 ++++++--------
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/include/linux/tick.h b/include/linux/tick.h
index b232ccc..532e650 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -56,7 +56,6 @@ struct tick_sched {
 	unsigned long			idle_jiffies;
 	unsigned long			idle_calls;
 	unsigned long			idle_sleeps;
-	int				idle_active;
 	ktime_t				idle_entrytime;
 	ktime_t				idle_waketime;
 	ktime_t				idle_exittime;
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 58e1a96..c4d7113 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -157,7 +157,7 @@ update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_upda
 {
 	ktime_t delta;
 
-	if (ts->idle_active) {
+	if (ts->inidle) {
 		delta = ktime_sub(now, ts->idle_entrytime);
 		ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
 		if (nr_iowait_cpu(cpu) > 0)
@@ -175,7 +175,6 @@ static void tick_nohz_stop_idle(int cpu, ktime_t now)
 	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 
 	update_ts_time_stats(cpu, ts, now, NULL);
-	ts->idle_active = 0;
 
 	sched_clock_idle_wakeup_event(0);
 }
@@ -186,7 +185,6 @@ static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
 
 	now = ktime_get();
 	ts->idle_entrytime = now;
-	ts->idle_active = 1;
 	sched_clock_idle_sleep_event();
 	return now;
 }
@@ -502,11 +500,11 @@ void tick_nohz_restart_sched_tick(void)
 	ktime_t now;
 
 	local_irq_disable();
-	if (ts->idle_active || (ts->inidle && ts->tick_stopped))
-		now = ktime_get();
 
-	if (ts->idle_active)
+	if (ts->inidle) {
+		now = ktime_get();
 		tick_nohz_stop_idle(cpu, now);
+	}
 
 	if (!ts->inidle || !ts->tick_stopped) {
 		ts->inidle = 0;
@@ -677,10 +675,10 @@ static inline void tick_check_nohz(int cpu)
 	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 	ktime_t now;
 
-	if (!ts->idle_active && !ts->tick_stopped)
+	if (!ts->inidle && !ts->tick_stopped)
 		return;
 	now = ktime_get();
-	if (ts->idle_active)
+	if (ts->inidle)
 		tick_nohz_stop_idle(cpu, now);
 	if (ts->tick_stopped) {
 		tick_nohz_update_jiffies(now);
-- 
1.7.5.4

[PATCH 3/2] nohz: Drop useless ts->inidle check before rearming the tick

[Frederic Weisbecker]

We only need to check if we have ts->stopped to ensure the tick
was stopped and we want to re-enable it. Checking ts->inidle
there is useless.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 kernel/time/tick-sched.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index c4d7113..5934aee 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -504,16 +504,14 @@ void tick_nohz_restart_sched_tick(void)
 	if (ts->inidle) {
 		now = ktime_get();
 		tick_nohz_stop_idle(cpu, now);
+		ts->inidle = 0;
 	}
 
-	if (!ts->inidle || !ts->tick_stopped) {
-		ts->inidle = 0;
+	if (!ts->tick_stopped) {
 		local_irq_enable();
 		return;
 	}
 
-	ts->inidle = 0;
-
 	rcu_exit_nohz();
 
 	/* Update jiffies first */
-- 
1.7.5.4

Re: [PATCH 1/2] nohz: Drop useless call in tick_nohz_start_idle()

[Frederic Weisbecker]

Ping? No problem with these three patches?

On Thu, Jul 21, 2011 at 08:49:36PM +0200, Frederic Weisbecker wrote:
> The call to update_ts_time_stats() there is useless. All
> we need is to save the idle entry_time.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
>  kernel/time/tick-sched.c |    3 ---
>  1 files changed, 0 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index d5097c4..58e1a96 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -185,9 +185,6 @@ static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
>  	ktime_t now;
>  
>  	now = ktime_get();
> -
> -	update_ts_time_stats(cpu, ts, now, NULL);
> -
>  	ts->idle_entrytime = now;
>  	ts->idle_active = 1;
>  	sched_clock_idle_sleep_event();
> -- 
> 1.7.5.4
> 

Re: [PATCH 1/2] nohz: Drop useless call in tick_nohz_start_idle()

[Frederic Weisbecker]

Forget these patches. Peterz found that the 2nd one is buggy and
I need to refine the others changelog.

Thnaks.

On Thu, Jul 21, 2011 at 08:49:36PM +0200, Frederic Weisbecker wrote:
> The call to update_ts_time_stats() there is useless. All
> we need is to save the idle entry_time.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
>  kernel/time/tick-sched.c |    3 ---
>  1 files changed, 0 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index d5097c4..58e1a96 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -185,9 +185,6 @@ static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
>  	ktime_t now;
>  
>  	now = ktime_get();
> -
> -	update_ts_time_stats(cpu, ts, now, NULL);
> -
>  	ts->idle_entrytime = now;
>  	ts->idle_active = 1;
>  	sched_clock_idle_sleep_event();
> -- 
> 1.7.5.4
>